The present invention pertains generally to an apparatus for turning boards through 180 degrees for inspection and grading purposes.
In the inspection and grading of sawn lumber, it is common practice to manually invert each board to inspect all surfaces and then stamp it with a grade mark. Turning boards to view top and bottom surfaces and edges entails considerable effort over the course of a work shift. For inspection and grading the lumber is transported on a continuously moving conveyor.
U.S. Pat. Ser. No. 4,484,675 is directed toward an apparatus for turning boards through 180 degrees against their conveyed direction of travel. An arm engages the leading edge of the board to tip same upwardly and rearwardly relative conveyor travel. In current grading operations, the spacing between successive boards and board speed is such that such rearward tipping could result in the board coming to rest on top of the following board as no provision is made for momentarily delaying the following board (s).
U.S. Pat. Ser. No. 3,426,882 is of interest in that it discloses chain carried arms which swing upwardly through a board path of a conveyor to cause board rotation. The mechanism is complex and also no provision is made for delaying the following board to prevent the turning of multiple boards.
U.S. Pat. Ser. No. 3,380,570 discloses an apparatus for inverting wood panels between a conveyor and a belt equipped tipple. The panels move into edgewise abutment with an arm assembly whereafter the arm is rotated upwardly through 90 degrees with the panel falling on to the tipple. The arms gravitate from a raised, vertical position to a position below the panel path. No provision is made for varying arm length or delaying a following panel.
By and large, boards are still manually turned in sawmills for inspection purposes which is indicative that known board turners or inverters do not accomplish the task in a suitable manner or are otherwise unacceptable for one reason or another.